One other point of interest is that these dynamic quests will have multiple stages, and different outcomes can trigger different quests. For example, perhaps in one quest you'll need to protect a scientist as he tries to summon magical energies into a golem... only for the golem to then go berzerk and start trashing his lab. Succeed in destroying the golem in time to save the lab, and you'll get a big reward. Fail, and you might have a follow-up quest to collect replacement parts to fix the lab. These are small details, but they reward you even if you don't successfully complete every single quest.
Guild Wars 2, next to other MMOs, feels vibrant and alive because of this. Whereas doing group quests in most MMOs often requires you to actively go out of your way, in Guild Wars 2, people congregate around these event hotspots. As most of your rewards and experience come from participating in these quests (and you receive more the more you participate), they naturally encourage cooperation, especially because many are balanced with larger groups of players in mind. This is the first MMO I've played where even complete strangers have been helpful and friendly more often than not - even if it's for ultimately selfish reasons.
Character System & Combat
Unfortunately, while Guild Wars 2 has a well-presesnted story and vibrant game world, the character system isn't quite as successful. The game has eight character classes: guardian, warrior, engineer, ranger, thief, elementalist, mesmer and necromancer. These should be pretty self-explanatory, as they map to very typical archetypes. All of the classes have fairly unique skills as well as bonus abilities. For example, as a necromancer, I was able to enter Death Shroud mode, which allowed me to use the special Life Force resource to fuel special attacks, while as a Ranger, I was able to summon a pet to help me in battle. These gimmicks are fun, but don't fundamentally change the way you play and all classes can solo most parts of the game as they have a very wide palette of abilities.
Leveling in Guild Wars 2 isn't quite the same as in some other MMOs. Each time you level up, you gain both a skill point and a trait point. Skill points are used to unlock, well, your active skills, which aren't presented in a traditional skill tree format, but instead divided into level-restricted tiers. Traits are your passive benefits, and you gain bigger "capstone" bonuses the more you invest into a particular one. Health, damage and other attributes scale automatically as you increase in level.
Most of the customization comes from your equipment, which is primarily responsible for increasing your attributes, but also determines the weapon skills you have available. Different weapon types give different skills which must be unlocked, but you'll manage to get them all pretty quickly. These skills tend to be honed for certain play-styles - for instance, my necromancer used daggers for a while due to their higher direct damage and life-stealing, but later I switched to staves due to their area-of-effect and support capabilities. This makes weapon choice more than just cosmetic, which is definitely appreciated when so many RPGs these days reduce weapon types to a single DPS number. The arguable downside is that there is little permanence in character building, though it could be said that it's a good thing considering how much time you'll need to spend with it.
The problem with Guild Wars 2, with respect to its character system, is that it lacks a good sense of progression. Part of this is to blame on the design of the skill system. Because of the way skills are divided into tiers and all skills on a given tier have equal cost, it's pretty easy to get the skills you want to use very early on, and by even around level 45 I had been using pretty much the exact same skills for several weeks with no problems, or modifications required later on - I switched out more due to boredom than necessity. The same issue applies with respect to the weapon skills, as once you've fully unlocked them after an hour or so, there is basically no progression on gear except for attribute increases as the game goes on.